A conventional high frequency power amplifier apparatus is described. As shown in FIG. 4, the conventional high frequency power amplifier apparatus has the following elements:                input terminal 1;        power amplifier 2 for receiving a signal that has been fed into input terminal 1;        directional coupler 3 for receiving an output from power amplifier 2;        output terminal 4 for receiving an output from directional coupler 3; and        automatic power control circuit 5 of which input portion 5a is connected to coupling output terminal 3a of directional coupler 3 and output portion 5b is connected to power control terminal 2a of power amplifier 2.        
Ground terminal 5c of automatic power control circuit 5 is connected to ground terminal 2b of power amplifier 2 through conductor 6 and then grounded.
Noise level is required to be low in a receiving band of an apparatus employing the high frequency power amplifier apparatus, but a noise characteristic of the receiving band is degraded in the conventional circuitry for the following reason. Since ground terminal 5c is connected to ground terminal 2b through conductor 6 and then grounded in this circuitry, noise generated by a signal from power amplifier 2 via automatic power control circuit 5 comes into power amplifier 2 through conductor 6 and ground terminal 2b and comes out of power amplifier 2 again, thereby degrading the noise characteristic.